Ok, here's the short list of things you'll need to do that aren't detailed on the protoslot website.
1. tear down your "donor" 908. use a flunder, long or short tail.
2. on the chassis pan, you'll need to cut most of the front edge back a couple of mm. the stiffening ribs that run almost all the way forward will have to be cut right down.
3. on the resin body, you'll need to trim the front and rear body posts a couple of mm. you can pierce the oil cooler air inlet very easily, and it looks good if you glue the front grille from the donor car there. the outlet on the bonnet will rimming from inside so it doesn't foul the top of the wires, as this point is right on top of the guide. you'll need a drill to drill some screwholes. I've not done this yet, but I'm planning on "tacking" the chassis in place with a small spot of superglue, then drilling.
4: the headlight glasses off the fly donor will need a lot of reshaping to get them to fit right. I didn't quite manage it.
5: it's a pain getting the tail end of the rear window to sit right in it's little spot.
6: as well as the holes it shows you to cut in the "interior/mechanicals" component, you'll need to cut off quite a lot on the corners of the bulkhead behind the driver, otherwise the body won't fit over it.
7: if you buy the painted kit, you'll still need to have some gloss white paint- the body has an extra part that forms the underside of the tail, and that's unpainted.
there's also no real location for the interior or the dashboard so you have to do it by eye a bit. this can be extra-tricky when you're trying to get the whole thing together.